Wednesday, November 9, 2016

Zeal E/PASO Communication Tool - part 2

In the first post about the Zeal E/PASO, we saw a bit of the history of personal computer network, and some informations about this communications terminal. In this post we'll see its insides and if it is or not a "hidden" MSX.

And What Is Inside Zeal E/PASO Communication Tool?

This is the board of Zeal E/PASO, it's very compact.

Magic. Pure Magic. That's what is inside this machine released in 1993 and sold until 1998. It's very easy to spot the Yamaha V9958 and the four RAM ICs (totalizing 128KB of VRAM), which means the E/PASO have the same video than a MSX2+, as other appliances that we saw before in this blog.

Yamaha V9958 and 128 512KB VRAM (4 x Hitachi HM514256)
(the RAM chips are all 256K x 4bits, but were used as if they have 64K x 4bits)

Close to the keyboard connectors we can see the MSX-SYSTEM chip. This Yamaha S3527 implements the PSG, PPI, slot handling and some additional logic. With it and the VDP checked, the only important piece missing to make a MSX is the Z80 processor.

Yamaha S3527 at top left, Hitachi HD64180RF6X at bottom
middle and, at right, a MaskROM and a EPROM.

And it's there, just behind the 12.288MHz crystal. It's a Hitachi HD64180RF-6X. It's a 16-bits processor made by Hitachi that keeps the compatibilty with Z80. It can run in "Z80" mode, which is almost the same of Z80 running at high speed, but it also have additional modes and could support up to 1MB without doing paging.

If we confirm that E/PASO is a MSX, it will not be the first using an enhanced Z80 as main processor. The first that comes to mind are the MSX TurboR machines, with the R800. But the A1GT and A1ST are not the only MSXs and not even the first ones to provide another CPU in addition to the Z80.

Victor released two MSX2 machines, the HC-90 and HC-95. Both are amazing machines with RS232C, video editing features, more memory and, of course, the turbo mode with the enhanced processor. They are the ultimate MSX2 machines.

The first item of this advertising from MSX Magazine 1987-04 translates to:
"(1) Turbo Mode to achieve the high-speed arithmetic processing"
Then it says that using the HD64180, running at 6.14MHz,
you will have 2.2 times the performance of other MSX2s.

The faster processor used by HC-90/95 is the HD64180, the same used by E/PASO. What E/PASO did first, is to use *only* the enhanced Z80.

There are some programs in the wild that uses some "bugs" and undocumented instructions of original Z80. Being a Z80 compatible, the HD64180 follows only the documented behavior of Z80, so the programs that uses the undocumented instructions won't work (or will freeze at random).

To have a high speed mode and the access the huge program library that the MSX have, the HC-90/95 have two processors: the HD64180 and a common Z80. You can select which processor will be active by a switch, at boot time. Changing the switch will choose the processor and the BIOS that will be used.

The MSX TurboR machines have two processors, too. With two advantages over HC-90/95: you can select between Z80 or R800 by software and at will, not only at boot time.

E/PASO was a appliance built to run only the built-in software. The upside of being a appliance was that it had no need to run all MSX software, which means that there was no need of a additional Z80 to solve any incompatibility between the some software and the HD64180. To save money and keep the design simple, the E/PASO can have only the HD64180 as its main processor.

At right of HD64180 processor, the E/PASO have a Hitachi HN62321 MaskROM, with 128KB, and a EPROM with a sticker saying "E/P ver1.00". I guess the Hitachi is the Kanji-ROM and the E/PASO software is in the EPROM. Good, that this EPROM is on a socket, that makes it easier to dump this software. I am very curious about what is inside this EPROM.

There is also two ICs labeled as "E/P 1" and "E/P 2", which I don't have any idea about what they are. At their left side we have a RAM chip, a Hyundai HY62256 with... 32KB. Seriously? This machine have only 32KB RAM!?!? This is the downside of being a appliance. A huge downside in my opinion, considering that this machine doesn't have a lot of internal space to put more RAM and almost no external expansion possibilities.

The modem circuitry is at PCB's left side. Looks like a separated world from the rest of PCB, and deserves it's own silk saying: "ZEAL MODEM". This world have a modem in a chip (IST SC11024CQ), which needs to be used in conjunction of a modem controller (IST SC11043CQ). This set have it's own clock and a 32KB RAM (another Hyundai HY62256). Next to the RAM there is another IC labeled as "E/P 3". Like the "E/P 1" and "E/P 2", I don't have idea of what the "E/P 3" is.

If we consider only the components used in Zeal E/PASO, it's a MSX based machine. But, as usual, we need to check the contents of E/PASO's EPROM, so we can confirm the MSX architecture.

Hi Piter, my name is Rafael, I am a Brazilian/Canadian and a MSX fan. I live in Vancouver and recently got a Sony MSX 2+ HB-F1XDJ from Japan. I am also a Computer Engineer and an Electronic Hobbyist, and I am working on a project of building one Z80 computer. Let me know if you would like to make contact.